This invention relates to a method for manufacturing multilayer ceramic capacitors including adjusting the capacitance thereof, and relates to the capacitor product made thereby that includes alternate overlapping electrodes plus at least one pair of coplanar capacitor-adjusting electrodes.
Multilayer ceramic capacitors typically include a ceramic block or body containing mutually parallel overlapping buried electrodes, the alternate of which extend to one body side face and the remaining buried electrodes extend to the opposite side face. Terminals are attached to the two opposite side faces contacting respectively these two groups of interdigitated mutually parallel buried electrodes. The total capacitance value C.sub.T obtained is predicted by the standard formula C.sub.T =KA.sub.o /t where K is the dielectric constant, A.sub.o is the total area of overlapping between oppositely polarized electrodes and t is the distance between adjacent overlapping electrodes, i.e. the thickness of the active ceramic dielectric between adjacent overlapping electrodes.
For a given target capacitance value, it is normally desirable to use a few rather than many overlapping electrodes by using as thin active dielectric layers as is practical, because of the high cost of electrode materials, e.g. silver and palladium.
But when a small capacitance value is sought and the number of overlapping electrodes is very few, to use one more or to use one less produces a large incremental change in total capacitance so that such a means becomes increasingly impractical for adjusting capacitance value as the number of overlapping electrodes decreases. An alternative is to manufacture a large number of such capacitors to a broad capacitance tolerance and sort out those that meet the tight tolerance. This is usually risky because of the large inventory of broad tolerance capacitors that is left for which no market may be found.
It is therefore an object of the present invention to provide a method for making small incremental adjustments in capacitance values of multilayer ceramic capacitors.
It is further an object of the present invention to provide a multilayer ceramic capacitor having, in addition to the conventional overlapping electrodes, at least one pair of capacitance adjusting coplanar electrodes.